That’s why they call ‘em ‘Restricted Waters’

That’s why they call ‘em ‘Restricted Waters’
During my third deployment to Rota Spain on Sea Trials I was an E-3 Seaman Gang member and a Helmsman/Planesman watch stander.(When I wasn't mess cookin') 
I was lucky enough to be mentor'd by 'one of the best' planesmen I was ever privileged to know, QM3/SS Jon Honnaker. Not known as one of the most demanding watch stations it still had 'a feel' to it that if you did your job right was fun. To be really good at anything you have to get that 'feel', too. I had it.
We were operating in the restricted waters in the Atlantic not too far from Rota. After several days of drills and spills we were in the short strokes just prior to pulling into port for a final top off and patrol deployment. 
During those final days after the shakedown was virtually complete was the traditional period we used to calibrate those EM logs.
Running in a straight line at normal patrol depth maintaining strict course and depth guidelines. No more than 1 degree from ordered course and no more than 6" from ordered depth. We didn't want to invalidate the cal's. We began with the lower speeds. 
As we progressed to the higher speeds the day passed into night. It was late and as we found out later the moon was full. 
The boat was trimmed well and the water temperature was fairly consistent. We were slipping through the water like a well lubricated phallic symbol through, well, you know. 
I was on the Fairwater planes and we were some fifteen minutes from making the turn back down the same lane. It was quiet and control was rigged for red. 
We were each in our own little worlds. Some non regulation discussions were in progress. Ships speed was 21knots+. 8000 tons of screaming nuclear powered steal haulin' it through the dark night waters of the mid atlantic off the coast of Spain. 
All of a sudden a loud thump was heard directly above our heads followed by a scrapping metal on metal sound and a whirring like a reel of fishing string paying out REAL fast. Then a very distinguishable tug could be felt and my angle indicator and depth gage started moving up toward the surface. It had only varied about 3" but with the strict depth requirements I was only 3" from invalidating the cal run. 
The order from the OOD came to "watch your depth planesman"
I applied several degrees of down angle on the Fairwater planes, 3 or 4, 
We all looked at each other, Jon the Diving officer and me, with puzzled looks on our faces, wondering "what the hey?" After several long seconds and four degrees of down angle on the planes another sound was heard. A snap. And the boat could be felt to lurch forward and the bow dropped back to a zero angle and I 'fell' back on ordered depth. We returned to our routine and later that night we went to periscope depth and took a visual of the area. As we were in restricted waters we were not surprised that no visible contacts were detected. At that speed nothing could be heard and no contacts were known to be around by using passive sonar techniques.
On surfacing the next morning and beginning the rigging of topside for maneuvering up to the pier we noticed a diagonal slice running from low starboard to high port about an inch across (I could put the side of my hand in the groove) and at least fifteen feet long across the front of the sail ending near the port fairwater plane. It had a strange look to it, almost like a cable. 
That morning we pulled back into Rota. On the pier were several well armed LaGuardia Seville and what looked like some town politico's. 
Word came down that the CO was about to be arrested for manslaughter! Of course after ten days of sea trials we were all right there to confirm his abuses on the crew.
As it turned out though a local fishing trawler had gone down the previous night while fishing in the restricted waters off the coast of Spain killing all five crew members and destroying a full half of the local fishing fleet. 
Local residents were up in arms. "Heads were going to roll". 
Obviously, it turns out, that the trawler had its nets out, the bottom of which were nearly 75ft (25 meters the same range our sail was at), the bottom of the nets have a large cable that holds the net down straight and helps keep it from tangling. 
We snagged that cable with our sail going the opposite direction or on some tangent of the trawlers course. The fishermen must have had a brief moment of elation in belief that they had just caught the largest fish in the world. In fact they had. 
Their elation must have equally quickly turned to terror as they realized this fish was going to eat their lunch.
The cable zipped across the front of our sail like a giant high speed rat tail file before we hit the end of it or it snapped or the trawler broke up and sank. Which it surely did. Killing all aboard. 
The only thing that saved the CO's bacon?
They don't call'em "restricted waters" for nothing.